John Dalton the solid sphere

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Transcript of John Dalton the solid sphere

SOLID SPHERE MODEL - JOHN DALTON Timeline: In 1803 John Dalton came up with a theory that was different than the ancient greeks theory it had chemical measurements to back it up. It wasn't just a logical statement that there are atoms because there has to be atoms. His atomic theory stating there must be tiny particles inside elements known as atoms. He said that the reason an element is pure is because all atoms of an element were identical and in that had the same mass. He stated that the reason why elements were different to other elements was because that the atoms were different from one another. In his therory he also said that compounds contaned atoms of different elements combined together, Becasuse compunds are pure substances, he had a theory that atoms of different elements were somehow bonded to one another, and they arn't easily seperated. Compounds have constant structure and because they contain a fixed ratio of atoms, and each atom has its own characteristic weight, and thus, having a weight ratio of one element to another. In saying that, he said that chemical reactions involve the rearrangement of pattern of those atoms. What he used as an example: The first compound will have one atom of A and one of B; the next, one atom of A and two atoms of B; the next, two atoms of A and one of B; and so on.Scientists before him, Democritus and Isaac Newton, they all had a similar theory. Democritus proposed the idea that all matter had small particles, he named them atoms. And Isaac Newton proposed a mechanical universe with small solid masses in motion. So, basically Dalton expanded on these theories and came up with his own. John's Theory 1803 - John Dalton Proposed an "atomic theory" with spherical solid atoms based upon measurable properties of mass.1832 - Michael Faraday Studied the effect of electricity on solutions, coined term "electrolysis" as a splitting of molecules with electricity, developed laws of electrolysis. Faraday himself was not a proponent of atomism.1859 - J. Plucker Built one of the first gas discharge tubes ("cathode ray tube").1869 - Dmitri Mendeleev Arranged elements into 7 groups with similar properties. He discovered that the properties of elements "were periodic functions of the their atomic weights". This became known as the Periodic Law.1873 - James Clerk Maxwell Proposed electric and magnetic fields filled the void.1879 - Sir William Crookes Discovered cathode rays had the following properties: travel in straight lines from the cathode; cause glass to fluoresce; impart a negative charge to objects they strike; are deflected by electric fields and magnets to suggest a negative charge; cause pinwheels in their path to spin indicating they have mass.1886 - E. Goldstein Used a CRT to study "canal rays" which had electrical and magnetic properties opposite of an electron.1894 - G.J. Stoney Proposed that electricity was made of discrete negative particles he called electrons ". 1895 - Wilhelm Roentgen Using a CRT he observed that nearby chemicals glowed. Further experiments found very penetrating rays coming from the CRT that were not deflected by a magnetic field. He named them "X-rays".1896 - Henri Becquerel While studying the effect of x-rays on photographic film, he discovered some chemicals spontaneously decompose and give off very pentrating rays.1897 - J.J. Thomson Used a CRT to experimentally determine the charge to mass ratio (e/m) of an electron =1.759 x 10 8 coulombs/gram.1897 - J.J. Thomson Studied "canal rays" and found they were associated with the proton H + .1898 - Rutherford Studied radiations emitted from uranium and thorium and named them alpha and beta.1898 Marie Sklodowska Curie Studied uranium and thorium and called their spontaneous decay process "radioactivity". She and her husband Pierre also discovered the radioactive elements polonium and radium.1900 - Soddy Observed spontaneous disintegration of radioactive elements into variants he called "isotopes" or totally new elements, discovered "half-life", made initial calculations on energy released during decay.1900 - Max Planck used the idea of quanta (discrete units of energy) to explain hot glowing matter.1903 - Nagaoka Postulated a "Saturnian" model of the atom with flat rings of electrons revolving around a positively charged particle.1904 - Abegg Discovered that inert gases had a stable electron configuration which lead to their chemical inactivity. 1905 - Albert Einstein Published the famous equation E=mc 21906 - Hans Geiger Developed an electrical device to "click" when hit with alpha particles.1909 - R.A. Millikan Oil drop experiment determined the charge (e=1.602 x 10 -19 coulomb) and the mass (m = 9.11 x 10 -28 gram) of an electron.1911 - Ernest Rutherford Using alpha particles as atomic bullets, probed the atoms in a piece of thin (0.00006 cm) gold foil . He established that the nucleus was: very dense,very small and positively charged. He also assumed that the electrons were located outside the nucleus.1914 - H.G.J. Moseley Using x-ray tubes, determined the charges on the nuclei of most atoms. He wrote"The atomic number of an element is equal to the number of protons in the nucleus". This work was used to reorganize the periodic table based upon atomic number instead of atomic mass.1919 - Aston Discovered the existence of isotopes through the use of a mass spectrograph.1922 - Niels Bohr Developed an explanation of atomic structure that underlies regularities of the periodic table of elements. His atomic model had atoms built up of sucessive orbital shells of electrons.1923 - de Broglie Discovered that electrons had a dual nature-similar to both particles and waves. Particle/wave duality. Supported Einstein.1927 - Heisenberg Described atoms by means of formula connected to the frequencies of spectral lines. Proposed Principle of Indeterminancy - you can not know both the position and velocity of a particle.1929 - Cockcroft / Walton Built an early linear accelerator and bombarded lithium with protons to produce alpha particles1930 - Schrodinger Viewed electrons as continuous clouds and introduced "wave mechanics" as a mathematical model of the atom. The Solid Sphere Timeline information:http://atomictimeline.net/index.php 1803 1832 1859 1869 1873 1879 1886 1894 1895 1896 1897 18981900 1903 1904 1905 1906 1909 1911 1914 1919 1922 1923 1927 1929 1930